Recovery of hydrocarbons from subterranean hydrocarbon-bearing formations

ABSTRACT

A process for the recovery of hydrocarbons from subterranean hydrocarbon-bearing formations by the treatment of the formation with an aqueous medium containing a base and a substituted nitrobenzene.

[72] Inventors David G. Feuerbacher [56] References Cited Helm"; UNITED STATES PATENTS 1 H [2]] App] gz'gzj 2,356,205 8/1944 Bla1r, Jr. et a1 166/305UX 9 9 2,813,583 11/1957 Marx eta] 166/271 [22] Wed 69 3108059 10/1963 0 Id 208/11 [45] Patented Jan.l2,]97l 3279538 10/1966 g 6 [73] Assignee Texaco Inc ,3 o sc er 16 /274 New York,N Y 3, 30,344 7/1967 Re1sberg... 166/273X acorporation ofnelaware 3,410,343 11/1963 AbdO 166/274 3,455,386 7/1969 Reisbergn. 166/275 3,490,532 1/1970 Carlin 166/275X 1 1 RECOVERY OF HYDROCARBONS FROM Primary Examiner-Stephen J. Novosad SUBTERRANEAN HYDR CA B Attorney-K. E. Kavanagh and Thomas H. Whaley FORMATIONS 26 Claims, No Drawings [52] U.S.C| 166/266, 166/272, 166/274, 208/11 [51] lnt.Cl ..E2lb 43/22,

E21b 43/24 ABSTRACT: A process for the recovery of hydrocarbons [50] Field oi'Search 166/266, from subterranean hydrocarbon-bearing formations by the 267, 265, 268, 274, 275, 272, 263, 305, 271; treatment of the formation with an aqueous medium contain- 208/1 1; 299/7; 252/8.55D ing a base and a substituted nitrobenzene.

SUBTERRANEAN HYDROCARBON-BEARING FORMATIONS FIELD OF THE INVENTION This invention relates to an improved process for the recovery of hydrocarbons from hydrocarbon-bearing formations. The process of this invention is particularly useful for increasing the recovery of low-gravity crude oils, oil from tar sands, and residual crudes in hydrocarbon-bearing formations, and is especially useful for recovery of residual hydrocarbons from form ations from which varying amounts of the more mobile fractions of the original hydrocarbons in place have been recovered.

DESCRIPTION OF THE PRIORART Among the most important problems related to the recovery of crude oils from porous matrices are the recovery of low-gravity crudes (less than 25 API), oils from tar sands, and the secondary recovery of crude oils containing high percentages of asphaltene and aromatic components. Some of the techniques that have been applied to these problems are water flooding, solvent flooding, and steaming. However, these techniques usually recover only a minor portion of the petroleum products present in the formation, and may leave up to 70 to 80 percent of the original hydrocarbons in place.

Of the improved recovery methods which permit additional recovery of hydrocarbons from partially depleted formations, water flooding is one of the more widely practiced processes. Although a successful water flood may result in recovery of 30 to 50 percent of the original hydrocarbons left in place, generally, the application of water flooding to heavy crudes results in much lower recoveries.

Newer developments in recovery methods for heavy crudes have included the use of steam injection, applied in several modifications, including the push-pull technique and through-put methods. Steam flooding processes have resulted in significant recoveries insome areas of heavy crude reservoirs. Improved recovery is believed to be at least in part due to the drastic viscosity reduction which is characteristic of heavy crudes that accompanies an increase in temperature whereby the mobility of the crude is improved.

However, the application of these recovery techniques to depleted formations may leave major quantities of crude unrecovered, particularly where the crude is tightly bound to the sand particles of the formation, that is, the absorptive capacity of the sand for the crude is great. Consequently, process modifications have been developed that incorporate additives to improve the efficiency of these processes such as the use of surface-active agents and miscible liquids that decrease the interfacialtension between the water and the reservoir crude.

In addition, additives to improve the wettability characteristies of the formation, may be used. For example, a dilute alkaline aqueous solution with or without surfactants is known to increase the wetting characteristics of sand surfaces, and promote a leaching action and emulsification of the tarry materials resulting in improved recovery.

However, the increase in recovery resulting from the application of these additive recovery processes to subterranean formations, particularly those containing low-gravity crudes, may be only minimal because of the nature of the crude and the strong association between its components and the surfaces of the sand formation.

SUMMARY This invention comprises displacing the hydrocarbons in a subterranean hydrocarbon-bearing formation or the oil in tar sands with an aqueous medium containing a base and a substituted nitrobenzene.

DESCRIPTION OF THE PREFERRED EMBODIMENT More specifically, it has been found that when an aqueous medium containing a base, e.g. an alkali metal hydroxide, and a substituted nitrobenzene, such as o-nitroanisole, is contacted with a hydrocarbon-bearing formation, of the hydrocarbons from the matrix occurs together with the formation of an oil-in-water emulsion, thereby enhancing the recovery of the hydrocarbons. It has also been found that a nonionic emulsifying agent may be incorporated in the aqueous medium so as to facilitate the formation of an oil-in-water emulsion. Furthermore, the use of a solubilizing agent in aqueous medium may in addition be preferred to improve the solubility of the substituted nitrobenzene.

Briefly, the method of the invention can be utilized as an improved water flood wherein the aqueous medium, described above, is employed as the flooding agent. Altemately, the method of invention may be utilized by the injection into a subterranean hydrocarbon-bearing formation via an injection well of a slug of the heretofore described aqueous medium containing a base and a substituted nitrobenzene, and thereafter injecting a drive agent, e.g. H O as water or steam, so as to drive the slug toward a producing well, from which the hydrocarbon is produced. In yet another application, the aqueous medium containing the base and substituted nitrobenzene can be used in an extractive technique in con junction with mined tar sands.

It is known that low-gravity crudes usually contain a higher percentage of asphaltenes than lighter crudes. The structure of petroleum asphaltics is quite complex. The result of recent work has indicated that asphaltenes appear to be a network of planar aromatic condensed rings. short aliphatic chains, and naphthenic ring structures. These asphaltene components apparently are capable of forming charge-transfer complexes both with themselves and with other compounds including nitrated aromatic compounds. It is believed that through the formation of charge-transfer complexes between the asphaltene components of the crude and substituted nitrobenzenes, such as o-nitroanisole, in an aqueous medium in accordance with this invention, the crude is effectively desorbed from the formation matrix and emulsified in the basic aqueous medium whereby its mobility is improved, leading to improved recovery. The base, e.g. an alkali metal hydroxide, serves not only to improve the wettability characteristics of the aqueous medium, but also improves the stability of the resulting oil-inwater emulsion.

The base is selected from the group consisting of the hydroxides of sodium, potassium, ammonium and mixtures thereof, and is used in a concentration in the range of about 0.001N to LON.

The substituted nitrobenzene which may be used for this process includes the mono-, di-, and trinitro substituted benzene, and mixtures thereof, wherein the substitution includes single, double, and triple substitution and the substituents are selected from the group consisting of methyl, ethyl, methoxy, ethoxy, hydroxy and combinations thereof. Concentrations of from about 500 ppm to about 5000 ppm are sufficient, but amounts outside this range may be employed if desired.

Illustrative of the invention, test runs were made in which an aqueous medium composed of a 0.1N aqueous solution of sodium hydroxide, and containing 500 ppm of the onitroanisole (ONA) was passed through a pack of 50-60 mesh glass beads containing a heavy crude (1 1 API) at an oil saturation of approximately 32 percent. Initially, three pore volumes of the displacing medium were passed through the pack during which time the displaced oil and effluent displacing medium were collected and the amount of displaced or extracted oil determined. The flood was then continued until either no more oil was displaced or until a total of twenty pore volumes of the displacing medium (including the first three) had been passed through the pack.

The following table shows that improved oil recovery was obtained by the method ofthis invention and that the presence of the substituted nitrobenzene, o-nitroanisole (ONA), resulted in about fifteen times more recovery than that obample of such a material is a water-miscible, nonionic surfactant of the hydroxyethylated, alkyl-aryl phenol category marketed by numerous manufacturers under such trade names as Surfonic-N, Triton-X," Retzanol-NP," etc. A preferred tained using the sodium hydroxide solution in the absence ofa Particular Surfactant of this category is surfohie substituted nitrobenzene. Furthermore, use of a sodium It will be pp from the foregoing description that the hydroxide aqueous solution containing either nitrobenzene or PmeeSS suhleet to other modifications Without departing anigole did not h i d il recovery from the scope of the invention as defined in the following In addition, other substituted nitrobenzenes that demonelalmsstrated improved oil recovery over that obtained using a sodiwe claim: um hydroxide aqueous solution included o-nitrophenol and A PieceSS for t r g hydrocarbons from a subternitrated mixed (m,p) cresols. The latter agent is a mixture of raheah Y tI-bca rmg formation which comprises conmono and trinitrated meta and para cresols' tacting said formation with an aqueous medium containing a In runs which were performed wherein a nonionic f base and a substituted nitrobenzene in amounts sufiicient to tant was incorporated into the solution containing sodium reduce the absorptive capacity of f formation for Said hydroxide and o-nitroanisole, an additional improvement in hydr?carbm enhanhe the moblhty t e thereby recovery was noted. forming an emulsion of said hydrocarbons in said formation The results also demonstrate that a solubilizing agent such ahd Said aqueous medium, recovering e emulsion thus as isopropyl alcohol, can be used in combination with the subformed and separating hydrocatbohs from said emulsloh' Smuted nitrobenzene Such as o njtroto]uene (ONT) to 2. The process of claim 1 wherein said base IS selected from crease the solubility of the substituted nitrobenzene and the hP eohslstlhg of the hydroxldes of Sodlum, potasslum thereby increase 0 recovery ammonium and mixtures thereof.

The tests demonstrated that the preferred location of the The ProeeSS of claim wherein said base is Contained in substituent relative to the nitro group is in the ortho position. the aqueous medlum Concentrations in the ange of from about 0.001N to LON.

Substituted Oil Total oil Total, nitrobenzene recovered recovered percent Additive cone. (p.p.n1.) (grams) (grams) recovery (1) Dist. water. None None 0 (2) 0.1 N aqueous NaOH. 0.19 0. 24 3.1 (3) Nitrobenzene 500 0.08 0.081 0.9 (4) Anisole... 2,000 0. 11 0. 11 1. 6 (5) ONA 500 0.48 3.04 42.6 (6) N-95 2 5,000 None None 0 (7) ONA 3 plus N-95. 1. 33 4. 14 44. 0 (8) ONA pit-1S N-95 l. 18 3. 74 49. 6 (0) ONT p us 5% isopropanol. 2, 000 0. 25 3. 22 41. 6 (l0) o-Nitrophenol 2, 000 0. 46 0. 56 6. 7 (11) Nitrated mixed (m,p) cresols 2, 000 0. 54 0. 70 8. 0

1 After 3 pore volumes through pack. 2 Jefferson Chemical Co. Surfonic N-95.

1 5,000 p.p.m. o-nitroanisole (ONA) plus 1,000 p.p.m. N-95 as an emulsion.

4 Saturated. 5 Repeat of above run.

NOTE.-In Runs 3 through 11, the additives were contained in 0.1 N aqueous NaOH.

in a preferred embodiment of the method of this invention, an injection well is drilled into a subterranean hydrocarbonbearing formation through which a slug of the aqueous medium containing the base and the substituted nitrobenzene as described above is injected into the formation. The slug is then followed by a subsequently injected aqueous drive agent, e.g. water. The size of the slug injected may vary within relatively wide limits, and will depend on a number of conditions, including the thickness of the formation, its characteristics, and the conditions for the subsequent injection of the aqueous drive medium. The aqueous drive agent may be H O in the form of either water or steam, the temperature of which may range up to 500 F.

in the passage of the aqueous medium through the subterranean hydrocarbon-bearing formation, hydrocarbons are desorbed from the formation, forming an oil-in-water emulsion which is then produced at production wells. Separation of the hydrocarbons from the emulsion is accomplished by one of several known emulsion breaking techniques.

Another embodiment of the method of this invention is illustrated in its application to the recovery of hydrocarbon materials from tar sands utilizing the aqueous medium in an extractive technique in combination with well-known techniques for the mining of the tar sand, and well-known techniques for the recover of the oil from the tar sand following its extraction.

in another modification of the process of this invention, an emulsifying agent capable of forming an emulsion and increasing the contact area may be incorporated in the aqueous medium. The ideal surface-active substance is one which acts to produce a relatively stable, homogeneous dispersion. An ex- 4. The process of claim 1 wherein the substituents of said substituted nitrobenzene are selected from the group consisting of methyl, ethyl, methoxy, ethoxy, and hydroxy and combinations thereof.

5. The process of claim 1 wherein said substituted nitrobenzene is selected from the group consisting of onitroanisole, o-nitrotoluene, o-nitrophcnol nitrated mixed (m,p) cresols and mixtures thereof.

6. The process of claim 1 wherein said substituted nitrobenzene is in the range from about 500 ppm to 5000 pp 7. The process of claim 1 including the addition of a nonionic emulsifying agent to said aqueous medium.

8. The process of claim 1 including the addition of a solubilizing agent to said aqueous medium 9. A process for recovering hydrocarbons from a subterranean hydrocarbon-bearing formation penetrated by an injection well and a production well, which comprises injecting into said formation through said injection well an aqueous medium containing a base and a substituted nitrobenzene in amounts sufficient to reduce the absorptive capacity of said formation for said hydrocarbons and enhance the mobility thereof, and thereafter injecting an aqueous drive medium into said formation through said injection well and driving the same toward said production well.

I0. The process of claim 9, wherein said base is selected from the group consisting of the hydroxides of sodium, potassium, ammonium and mixtures thereof.

11. The process of claim 10, wherein said base is contained in the aqueous medium in concentrations in the range of from about 0.001N to LON.

12. The process of claim 9 wherein the substituents of said substituted nitrobenzene are selected from the group consisting of methyl, ethyl, methoxy, ethoxy, and hydroxy and combinations thereof. I

13. The process of claim 9 wherein said substituted nitrobenzene is selected from the group consisting of onitroanisole, o-nitrotoluene, o-nitrophenol nitrated mixed (m,p) cresols and mixtures thereof.

14. The process of claim 9 wherein said substituted nitrobenzene is in the range from about 500 ppm to 5000 pp 15. The process ofclaim 9 wherein said aqueous drive medium is H 0.

16. The process of claim wherein the H O'is water, steam, and mixtures thereof, the temperatures thereof being fixed by optimum conditions of operation.

17. The process of claim 9 including the addition of a nonionic emulsifying agent to said aqueous medium.

18. The process of claim 9 including the addition of a solubilizing agent to said aqueous medium.

19. A process for recovering hydrocarbons from a hydrocarbon-bearing sand matrix having heretofore undergone mining processing, which comprises contacting said hydrocarbonbearing sand matrix with an aqueous medium containing a base and a substituted nitrobenzene thereby forming an emulsion of said hydrocarbons in said sand matrix and said aqueous medium, recovering the emulsion thus formed, and separating hydrocarbons from said emulsion.

20. The process of claim 19 wherein said base is selected from the group consisting of the hydroxides of sodium, potassium, ammonium and mixtures thereof.

21. The process of Claim 20 wherein said base is contained in the aqueous carrier in concentrations in the range of from about 0.001N to LON.

22. The process of claim 19 wherein the substituents of said substituted nitrobenzene are selected from the group consisting of methyl, ethyl, methoxy, ethoxy, and hydroxy and combinations thereof.

23. The process of claim 19 wherein said substituted nitrobenzene is selected from the group consisting of onitroanisole, o-nitrotoluene, o-nitrophenol nitrated mixed (m,p) cresols and mixtures thereof.

24. The process of claim 19 wherein said substituted nitrobenzene is in the range from about 500 ppm to 5000 ppm by volume.

25. The process of claim 19 including the addition of a nonionic emulsifying agent to said aqueous medium.

26. The process of claim 19 including the addition of a solubilizing agent to said aqueous medium, 

2. The process of claim 1 wherein said base is selected from the group consisting of the hydroxides of sodium, potassium, ammonium and mixtures thereof.
 3. The process of claim 2, wherein said base is contained in the aqueous medium in concentrations in the range of from about 0.001N to 1.ON.
 4. The process of claim 1 wherein the substituents of said substituted nitrobenzene are selected from the group consisting of methyl, ethyl, methoxy, ethoxy, and hydroxy and combinations thereof.
 5. The process of claim 1 wherein said substituted nitrobenzene is selected from the group consisting of o-nitroanisole, o-nitrotoluene, o-nitrophenol nitrated mixed (m,p) cresols and mixtures thereof.
 6. The process of claim 1 wherein said substituted nitrobenzene is in the range from about 500 ppm to 5000 ppm.
 7. The process of claim 1 including the addition of a nonionic emulsifying agent to said aqueous medium.
 8. The process of claim 1 including the addition of a solubilizing agent to said aqueous medium.
 9. A process for recovering hydrocarbons from a subterranean hydrocarbon-bearing formation penetrated by an injection well and a production well, which comprises injecting into said formation through said injection well an aqueous medium containing a base and a substituted nitrobenzene in amounts sufficient to reduce the absorptive capacity of said formation for said hydrocarbons and enhance the mobility thereof, and thereafter injecting an aqueous drive medium into said formation through said injection well and driving the same toward said production well.
 10. The process of claim 9, wherein said base is selected from the group consisting of the hydroxides of sodium, potassium, ammonium and mixtures thereof.
 11. The process of claim 10, wherein said base is contained in the aqueous medium in concentrations in the range of from about 0.001N to 1.ON.
 12. The process of claim 9 wherein the substituents of said substituted nitrobenzene are selected from the group consisting of methyl, ethyl, methoxy, ethoxy, and hydroxy and combinations thereof.
 13. The process of claim 9 wherein said substituted nitrobenzene is selected from the group consisting of o-nitroanisole, o-nitrotoluene, o-nitrophenol nitrated mixed (m,p) cresols and mixtures thereof.
 14. The process of claim 9 wherein said substituted nitrobenzene is in the range from about 500 ppm to 5000 ppm.
 15. The process of claim 9 wherein said aqueous drive medium is H2O.
 16. The process of claim 15 wherein the H2O is water, steam, and mixtures thereof, the temperatures thereof being fixed by optimum conditions of operation.
 17. The process of claim 9 including the addition of a nonionic emulsifying agent to said aqueous medium.
 18. The process of claim 9 including the addition of a solubilizing agent to said aqueous medium.
 19. A process for recovering hydrocarbons from a hydrocarbon-bearing sand matrix having heretofore undergone mining processing, which comprises contacting said hydrocarbonbearing sand matrix with an aqueous medium containing a base and a substituted nitrobenzene thereby forming an emulsion of said hydrocarbons in said sand matrix and said aqueous medium, recovering the emulsion thus formed, and separating hydrocarbons from said emulsion.
 20. The process of claim 19 wherein said base is selected from the group consisting of the hydroxides of sodium, potassium, ammonium and mixtures thereof.
 21. The process of Claim 20 wherein said base is contained in the aqueous carrier in concentrations in the range of from about 0.001N to 1.ON.
 22. The process of claim 19 wherein the substituents of said substituted nitrobenzene are selected from the group consisting of methyl, ethyl, methoxy, ethoxy, and hydroxy and combinations thereof.
 23. The process of claim 19 wherein said substituted nitrobenzene is selected from the group consisting of o-nitroanisole, o-nitrotoluene, o-nitrophenol nitrated mixed (m,p) cresols and mixtures thereof.
 24. The process of claim 19 wherein said substituted nitrobenzene is in the range from about 500 ppm to 5000 ppm by volume.
 25. The process of claim 19 including the addition of a nonionic emulsifying agent to said aqueous medium.
 26. The process of claim 19 including the addition of a solubilizing agent to said aqueous medium. 